1. Field of the Invention
The present invention relates generally to lifetime management devices and lifetime management methods.
2. Description of the Related Art
Inexpensive large-capacity flash memories, in particular, NAND flash memories, are commonly used in image forming apparatuses, such as printers, copiers, and multifunction peripherals, as a memory for storing optional program codes (hereinafter, “optional program”), user data pertaining thereto, and the like.
A NAND flash memory has a physical limitation that the number of program/erase cycles (hereinafter, “P/E cycle count”) per block is limited. When a P/E cycle count exceeds this limit, a read disturb error (i.e., a decrease in data retention capability) or a state (referred to as “bad block”) where data cannot be written normally will occur. Accordingly, as the P/E cycle count increases, the NAND flash memory approaches a state where the NAND flash memory cannot be used normally or, in short, end of device life.
Because product useful life (product lifetime) of an image forming apparatus is relatively long, there can be a case where a memory for storing optional programs, user data, and the like reaches its end of life before the product reaches its end of life. In such a case, if a user continues using the product without noticing that the memory has reached its end of life, loss of the optional programs, user data, and the like can occur. Accordingly, it is desired to manage lifetime of the memory appropriately.
For SSDs (Solid State Drives), eMMCs (embedded MultiMedia Cards), and the like, a mechanism that informs a user of a P/E cycle count, the number of bad blocks, and the like using management information referred to as SMART (Self-Monitoring, Analysis and Reporting Technology) information and urges the user to make replacement or the like before the memory reaches its end of life as a device is provided. However, not all NAND flash memories have a mechanism that informs a user of management information, such as the SMART information. For example, as for USB (Universal Serial Bus) memories and SD cards, because management information is not defined in a standard, a user generally cannot obtain such information, e.g., the P/E cycle count and the number of bad block described above.
Japanese Unexamined Patent Application Publication No. 2012-088937 (Patent Document 1) describes a technique that, when a bad block occurs during data writing to a NAND flash memory, acquires bad-block-occurrence-related information pertaining to occurrence of the bad block and stores the information in a non-volatile storage. According to the technique described in Patent Document 1, a flag indicating that the NAND flash memory is unrecyclable is stored in the non-volatile storage when the number of bad blocks in the NAND flash memory exceeds a tolerance or when bad blocks occur at intervals shorter than a tolerance, so that whether or not the NAND flash memory is recyclable can be distinguished.
However, although the technique described in Patent Document 1 enables distinguishing whether or not the NAND flash memory is recyclable, the technique does not tell when the NAND flash memory will reach its end of life. Accordingly, there is room for improvement in terms of appropriate management of the NAND flash memory.